TAMPA, Fla. — Alex Rodriguez erased personal doubts about regaining his power with one big swing Wednesday.

Rodriguez hit his first home run since returning to the Yankees following a drug suspension and Chris Capuano was forced out in the first inning by a quadriceps injury in New York’s 10-6 loss to the Boston Red Sox.

Mookie Betts had three hits for the Red Sox and is hitting .400.

“He’s an exciting player,” Red Sox Manager John Farrell said. “He works deep counts, he gets on base. What’s he shown in the minor leagues is starting to play out at the big league level.”

Rodriguez, meanwhile, said he was very happy and hadn’t hit a ball like that in a long while.

“Again, it’s early March. We’ll see what happens,” Rodriguez said. “You have to do that in New York, where it counts. It’s definitely a building block.”

Rodriguez hit a long drive to left-center on a 3-1 pitch from right-hander Brandon Workman leading off the fourth inning. Rodriguez has five hits in 11 at-bats (.455) this spring training.

“Very happy,” Yankees co-chairman Hank Steinbrenner said. “I’m not surprised with the hitting. … It’s encouraging. Hopefully it continues.”

Rodriguez has seen the number of fans booing him decrease daily. He received a partial standing ovation after his homer.

“The great reception I’ve been getting from the fans, that’s been a pleasant surprise,” Rodriguez said.

Rodriguez who turns 40 in July, hasn’t played a full season since 2007 because of a season-long drug suspension, operations on both hips and other injuries.

Rodriguez said a pregame talk with Yankees special adviser Gene Michael provided “good words of wisdom.”

“I just told him I think he can hit. He knows how to hit. He just needs a lot of at-bats, but I think that’s coming,” Michael said. “He’s already shown that he can get the bat to the ball. He’s not far off.”

Rodriguez made his second start at third base and cleanly handled two chances in five innings. The Yankees say Chase Headley is their starting third baseman and Rodriguez will be primarily a designated hitter.

Capuano, the top candidate to be the Yankees’ fifth starter, left after hurting his right leg while covering first base on Brock Holt’s one-out grounder to first baseman Garrett Jones. Capuano underwent an MRI exam.

“I’d be surprised if he’s not down for a while,” Manager Joe Girardi said.

Adam Warren and Esmil Rogers are among those to get additional consideration for the fifth starter spot if Capuano isn’t ready for the beginning of the season.

Travis Shaw opened the third inning with a first-pitch homer off Yankees reliever Andrew Miller, and also drove in two with a double during a four-run fourth.

Joe Kelly, the Red Sox starter, gave up two runs, three hits, one walk and struck out four in three innings.

“For the most part I made pitches but didn’t exactly put the ball where I wanted to,” Kelly said. “But for the second time out I felt pretty good about my stuff.”

Clay Buchholz is scheduled to start Thursday for Boston against Pittsburgh right-hander A.J. Burnett at Bradenton, Florida.

Also, Red Sox outfielder Rusney Castillo (strained left oblique) hit off a tee and took soft toss.

There has been no date announced when he will take on-field batting practice.

Masahiro Tanaka will make his first start Thursday night for the Yankees against Atlanta. He missed 21/2 months while rehabilitating a partially torn ulnar collateral ligament in his right elbow and returned for two late September starts.

“He’s been great,” General Manager Brian Cashman said.